Employee Benefits (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Defined Benefit Pension Plan [Member]
Components of net periodic benefit cost
Service cost	$ 299	$ 274
Interest	314	324
Expected return on plan assets	(470)	(410)
Recognized prior service cost (benefit)	(26)	(26)
Recognized net actuarial losses	158	184
Net periodic benefit cost	275	346
Supplemental Insurance/ Retirement Plan [Member]
Components of net periodic benefit cost
Service cost	381	356
Interest	267	231
Recognized prior service cost (benefit)	29	29
Recognized net actuarial losses	129	84
Net periodic benefit cost	$ 806	$ 700